Assessment of the Effects of Inspiratory Muscle Training (IMT) and Aerobic Training on the Quality of Life of Patients with Chronic Obstructive Pulmonary Disease.

Background: Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality worldwide. The aim of this study was to investigate the effects of inspiratory muscle training (IMT) and aerobic exercise on health-related quality of life of patients with COPD. Materials and Methods: This randomized controlled clinical trial was conducted on 60 patients with moderate to severe COPD, who were referred to Imam Hossein Hospital of Tehran, Iran in 2016. The patients were randomly assigned to four groups and treated for eight weeks. Group 1 (n=16) participated in 16 sessions of IMT (15 minutes per session), group 2 (n=14) performed aerobic exercises twice a week (40 minutes per session), group 3 (n=15) performed IMT and aerobic exercises, and group 4 (n=15) received no intervention, except for routine treatments (control). Quality of life was evaluated based on the Saint George’s Respiratory Questionnaire (SGRQ) at baseline, week 4, and week 8 after the intervention. Results: After eight weeks, all four groups experienced a significant improvement in their quality of life (P<0.05), and group 3 (IMT and aerobic exercise) showed the greatest improvement. However, quality of life improvement in group 4 (control) was less than the other three groups (P<0.05). Conclusion: Aerobic exercise and IMT were more effective than routine protocols in improving the quality of life of COPD patients. Furthermore, short-term IMT plus aerobic exercise had the greatest impact on improving the health-related quality of life of COPD patients and could be used in the management of these patients.


INTRODUCTION
Chronic obstructive pulmonary disease (COPD) is a set of physiological disorders associated with the obstruction of airways (1). The characteristic feature of COPD is persistent airway obstruction that is usually progressive (2). The most common sign of COPD is dyspnea, which limits exercise and physical activity in patients and leads to chronic avoidance behaviors towards physical activity (3).
COPD affects 4-6% of the world's population and is one of the leading causes of mortality worldwide. It is also the fourth cause of mortality in the United States (4).
Due to peripheral airway obstruction in COPD, air volume may be trapped in the lungs (hyperinflation). The TANAFFOS respiratory rate may be increased because inspiration occurs before the air is released from the lungs. Moreover, rapid shallow breathing leads to respiratory muscle fatigue and inefficient gas exchange; therefore, patients with COPD show signs of dyspnea (5). Previous studies have shown that dyspnea is associated with symptoms of depression, anxiety, fatigue, sleep disturbances, pain, and decreased quality of life (QOL) (6,7).
Patients with COPD show an initial increase in lactic acidosis during exercise and are unable to meet their ventilation needs. Therefore, interventions that improve ventilation, such as inspiratory muscle training (IMT), have the potential to reduce dyspnea and improve exercise tolerance in these patients. On the other hand, low levels of physical activity play a role in deconditioning of skeletal muscles and reducing exercise tolerance, which negatively affects QOL (4). Considering the insidious and progressive nature of COPD, pulmonary function may be easily lost by 50% before the emergence of symptoms. Sudden acute exacerbation of symptoms can affect the patients' QOL and treatment costs. Therefore, the main goal of COPD management and treatment is to improve the symptoms and QOL (5).
Pulmonary rehabilitation, including sports training, education, nutritional interventions, and mental support, is the standard care for patients with COPD (8). Respiratory exercises using IMT and exercise programs are components of pulmonary rehabilitation and are used to improve respiratory function and COPD management. In recent years, there have been few studies on the use of IMT in COPD patients. A meta-analysis of randomized controlled trials (RCTs) in patients with COPD revealed that IMT, as an independent treatment, improves the function (strength and endurance) of respiratory muscles, alleviates the symptoms of dyspnea, and improves exercise tolerance (9).
Aerobic exercise training is considered an essential component of pulmonary rehabilitation (10). Also, measurement of QOL is important for clinical decisionmaking. It has been observed that respiratory exercises improve QOL and dyspnea (11,12). Nevertheless, the effectiveness of IMT as a complement to general exercise remains uncertain. Although IMT results in significant improvements in respiratory muscle performance, its effects on pulmonary function, clinical outcomes, and QOL have not been confirmed by scientific evidence (13,14).
Despite the cost-effective and non-invasive nature of exercise therapy and IMT, there are limited studies on the effectiveness of these methods in improving the QOL of patients with COPD. Therefore, the aim of this study was to determine the effectiveness of conventional aerobic exercises and respiratory muscle training in improving the QOL of patients with COPD.

Intervention
Patients were randomly divided into four groups with an age adjustment of 10 years (from 30 to 69 years) and were treated for eight weeks. A total of 68 patients were divided into four groups, each consisting of 17 patients.
After the follow-up and post-training assessment, eight patients were removed from the study due to loss to follow-up. Finally, 60 patients were included in the study.

Patient evaluation
The standard Saint George's Pulmonary Disease Questionnaire (SGRQ) (  *Data are presented as mean±SD or frequency (%)**Significance at p≤0.05.

CONCLUSION
The results of the present study showed that all three treatments (for eight weeks) could improve the QOL of patients with COPD. However, the effectiveness of aerobic exercise plus IMT was greater than the control group. Also, combination of aerobic exercise with IMT had the greatest effects on the QOL of patients. Considering the high efficacy of aerobic exercise and IMT in improving the QOL of patients with moderate to severe COPD and the lowcost, non-invasive, and non-pharmaceutical nature of these methods, we can take an effective step in improving the health and QOL of these patients by encouraging them to use these methods. However, since limited studies have compared aerobic exercise, IMT, and combination of these two methods in the treatment of COPD patients, it is necessary to conduct more studies in the future to identify the best treatment option.